The present invention relates generally to vascular filters, and more particularly to vascular filters that may be deployed within a blood vessel and subsequently recovered, and to apparatus and methods for filtering a blood vessel during an endovascular procedure using such filters.
A number of endovascular procedures are presently performed on patients with atherosclerotic disease and the like to treat stenotic or occluded regions within the patient""s blood vessels, such as the coronary, carotid or cerebral arteries. For example, an angioplasty procedure may be used to dilate a stenosis, or an atherectomy may be performed to open severely occluded regions. A stent or other prosthesis may be implanted to retain patency of a vessel, either alone or in conjunction with these procedures.
One of the problems with these procedures, however, is that embolic material may be released from the wall of the vessel during the procedure, and travel downstream where it may become lodged or otherwise cause harm to the patient. For example, ischemic stroke may occur when such emboli are released in the carotid or cerebral arteries and travel to the patient""s brain.
To prevent or minimize damage from emboli, vascular filters have been suggested that are generally mounted on a device, such as a catheter, a guidewire, or a sheath. These devices may be introduced within a blood vessel downstream of a location being treated, and the filter on the device deployed across the vessel to capture embolic material released during a procedure, such as one of the procedures above. Upon completion of the procedure, the filter is collapsed, and the device removed from the patient.
These filter devices are generally introduced endoluminally over a rail, such as a guidewire, that is also used subsequently to introduce one or more surgical tools or other devices used to perform the procedure. During the advancement of these subsequent devices, the rail may be pushed and pulled axially within the vessel, causing the deployed filter to move back and forth. This movement of the filter may damage the vessel intima, may release embolic material captured by the filter, and/or may damage the structure of the filter itself.
Implantable filter devices have also been suggested that may be deployed, expanded and released within vessels, such as vena cava filters. These filter devices may not recovered, or may remain within the vessel for extended periods of time, where they may eventually become obstructed with thromboses, clots, emboli and the like, and harm the patient.
Therefore, there is a need for a vascular filter that may be deployed to capture embolic material with minimal risk of damage to the vessel and patient and/or that may be may be more easily recovered from the patient.
The present invention is directed to vascular filters that may be reversibly deployed within a blood vessel and subsequently recovered, and to apparatus and methods for filtering a blood vessel using such filters. In accordance with one aspect of the present invention, a vascular filter is provided that includes a tubular member having a proximal end and a distal end, and including a lumen for receiving a guidewire therethrough. An expandable frame is attached to the tubular member, the expandable frame being capable of assuming a collapsed condition and an enlarged condition. Filter material is attached to the expandable frame, the filter material having an open proximal end when the expandable frame assumes its enlarged condition.
A connector may be provided on the proximal end of the tubular member for detachably securing the vascular filter to a delivery device. In a preferred form, the expandable frame includes a plurality of struts, each of the struts including an intermediate region biased to bow outward from the tubular member, the proximal end of the filter material being attached to the intermediate region.
The vascular filter may be incorporated into an apparatus for filtering a blood vessel that includes the vascular filter, a tubular sheath, and an elongate retrieval member. The tubular sheath has a proximal end, a distal end for insertion into a blood vessel, and a lumen having an outlet at the distal end. The lumen preferably has a size for slidably receiving the vascular filter therein when the expandable frame is in its collapsed condition.
The retrieval member has a distal end deployable from the distal end of the tubular sheath, and a connector on its distal end for securing the tubular member thereto. In a preferred form, the retrieval member includes a recess in its distal end, and the mechanical connector is an expandable member in the recess.
The apparatus may be used in a method for filtering a blood vessel during an endovascular procedure. A vascular filter, such as that described above, is provided that includes an expandable frame and filter material disposed on a tubular member, the expandable frame being constrained in a collapsed condition. The vascular filter may be provided within a lumen of a tubular sheath, the tubular sheath constraining the frame in its collapsed condition.
A guidewire is placed within a blood vessel across a treatment site with its distal end at a location downstream thereof. The tubular member is advanced over the guidewire, with the expandable frame in its collapsed condition, to the location downstream of the treatment site. The expandable frame is expanded to its enlarged condition to open the filter material across the blood vessel, the guidewire remaining slidable within the tubular member. For example, the expandable frame may be biased to assume its enlarged condition, and the expandable frame may expand automatically when the vascular filter is deployed from the lumen of the tubular sheath.
An endovascular procedure may be performed at the treatment site, the vascular filter capturing embolic material released during the procedure. The procedure may involve advancing one or more surgical instruments or other devices over the guidewire. A retrieval member is then advanced endovascularly to the location downstream of the treatment site, preferably over the guidewire. The vascular filter is secured to the retrieval member, and the vascular filter and retrieval member are withdrawn from the blood vessel. Preferably, the expandable frame is directed to its collapsed condition before withdrawing the vascular filter and retrieval member from the blood vessel. For example, the retrieval member may include a tubular sheath having a lumen therein, and the expandable frame may be directed to its collapsed condition by withdrawing the vascular filter into the lumen of the tubular sheath.
Preferably, the tubular member is secured to the retrieval member with a mechanical connector on the retrieval member, such as the recess and expandable member described above. The retrieval member is manipulated until the proximal end of the tubular member is received in the recess, and then the expandable member is expanded to constrict the recess and thereby engage the proximal end of the tubular member. Alternatively, the mechanical connector may be a shrinking collar or collet device provided on the end of the retrieval member, that may grab the tubular member, for example, by receiving the tubular member in the collar and then reducing the collar diameter to secure the tubular member to the retrieval member.
An important feature of the present invention is that the vascular filter, when deployed within a blood vessel, slidably engages the guidewire used to deliver it. When subsequent devices are advanced over the guidewire, they may cause the guidewire to move back and forth within the vessel, but may not affect the deployed vascular filter, as the guidewire may simply slide back and forth within the tubular member. Thus, this slidable arrangement substantially reduces the risk of damage to the vessel that may be caused by inadvertent movement of the deployed vascular filter, as well as reducing the risk of damage to the filter itself.
Further, because the guidewire remains within the tubular member during the procedure, a retrieval device may be easily introduced into the vessel to recover the vascular filter. There is no need to hunt around within the vessel to locate the vascular filter, as the retrieval device may simply be advanced over the guidewire and into proximity with the vascular filter, thereby facilitating its withdrawal from the patient""s body.
Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.